JP2003234503A - Semiconductor light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting device that reduces dislocation density, and has high luminous efficiency. <P>SOLUTION: A foundation layer 13 for composing a semiconductor light- emitting device 20 contains Al, and-consists of a nitride semiconductor having a dislocation density of 10<SP>11</SP>/cm<SP>2</SP>or less. Additionally, n- and p-type conductive layers 14 and 17 are composed of a nitride semiconductor that has a small content of Al as compared with the nitride semiconductor and has a dislocation density of 10<SP>10</SP>/cm<SP>2</SP>or less. Furthermore, a luminous layer 15 is composed of a nitride semiconductor that has a small content of Al as compared with the nitride semiconductor and has a dislocation density of 10<SP>10</SP>/cm<SP>2</SP>or less. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device using a group III nitride which can be suitably used as a photodiode or the like.

[0002]

2. Description of the Related Art Group III nitride films are used as semiconductor films for semiconductor light emitting devices, and in recent years, particularly high brightness light sources for green light to blue light, and further,
It is also expected as a light source for ultraviolet light and white light.

In recent years, as a substrate for forming such a group III nitride film, a so-called epitaxial substrate having a base film formed by epitaxial growth on a predetermined base material is frequently used. Then, a predetermined group III nitride layer group formed by laminating a single layer group III nitride film or a plurality of group III nitride films is formed on this epitaxial substrate by using the MOCVD method or the like, The desired semiconductor light emitting device is obtained.

FIG. 1 is a block diagram showing an example of a conventional so-called PIN type semiconductor light emitting device.

In the semiconductor light emitting device 10 shown in FIG. 1, a GaN buffer layer 2 and a Si-doped n-G are provided on a substrate 1 mainly made of sapphire single crystal.
An underlayer 3 made of aN, an n-type conductive layer 4 made of Si-doped n-AlGaN, a light emitting layer 5 made of InGaN having a multiple quantum well (MQW) structure, and Mg-doped p-AlGa.
P-type cladding layer 6 made of N, Mg-doped p-GaN
The p-type conductive layer 7 made of is formed in this order. Figure 1
In the semiconductor light emitting device 10 shown in FIG. 3, the n-type conductive layer 4 to the p-type conductive layer 7 form a light emitting device structure.

A part of the n-type conductive layer 4 is exposed, and an n-type electrode 8 of Al / Ti or the like is formed on this exposed portion, and Au / Ni or the like is formed on the p-type conductive layer 7. A p-type electrode 9 is formed.

Then, by applying a predetermined voltage between the n-type electrode 8 and the p-type electrode 9, recombination of carriers occurs in the light emitting layer 5, and light of a predetermined wavelength is emitted. The wavelength is determined by the structure and composition of the light emitting layer.

[0008]

In the semiconductor light emitting device 10 shown in FIG. 1, the buffer layer 2 includes the substrate 1 and the base layer 3.
In order to compensate for the difference in lattice constant between and, and to enable epitaxial growth of the underlayer 3 to be formed above the substrate 1,
It functions as a buffer layer. Therefore,
Normally, ignoring its crystallinity, it is formed in an amorphous state at a low temperature of 500 to 700 ° C.

As a result, a relatively large amount of dislocations are contained in the buffer layer 2, and some of these dislocations are threading dislocations, which are the underlying layer 3, the n-type conductive layer 4, the light-emitting layer 5, and the p-type cladding layer. 6 and the p-type conductive layer 7. As a result, dislocations in excess of 10 ¹⁰ / cm ² were included in these layers, and the crystal quality was deteriorated. In particular, a semiconductor light emitting device for short wavelength, that is, the n-type conductive layer 3
The above tendency becomes remarkable when the light emitting layer 4 contains more Al.

When a semiconductor light emitting device is composed of such a layer having high dislocations and low crystal quality, there is a problem that so-called non-radiative recombination occurs due to the dislocations in the light emitting layer and the luminous efficiency is reduced.

An object of the present invention is to provide a semiconductor light emitting device having a reduced dislocation density and a high luminous efficiency.

[0012]

[Means for Solving the Problems] In order to achieve the above object,
The semiconductor light emitting device of the present invention comprises a base layer made of a nitride semiconductor and a light emitting device structure including a group of nitride semiconductor layers on a predetermined substrate, and the nitride semiconductor constituting the base layer is at least In addition to containing Al, the dislocation density is 10 ¹¹ / cm ² or less, and the nitride semiconductor layer group forming the light emitting device structure contains Al in a smaller content than the nitride semiconductor forming the underlayer. In addition to the above, the dislocation density is 1 × 10 ¹⁰ / cm ² or less.

The inventors of the present invention have made extensive studies to achieve the above object. The above-mentioned deterioration of the luminous efficiency is caused as a result of high dislocations based on the low crystal quality of each layer constituting the semiconductor light emitting device.
An attempt was made to improve the crystal quality by reducing the dislocation amount of each layer constituting the semiconductor light emitting device.

As described above, the dislocations in each layer constituting the semiconductor light emitting device are caused by the low crystal quality buffer layer. In the conventional semiconductor light emitting device shown in FIG. 1, since sapphire single crystal is used as the substrate 1 and n-GaN is used as the underlayer 3, n-nitride which is a group III nitride is formed on the underlayer 3. When the n-type conductive layer 4 made of AlGaN is formed, there is a problem that dislocations existing in the underlayer 3 propagate to the n-type conductive layer 4. In particular, n-AlGa forming the n-type conductive layer 4
When the Al content in N was increased, cracks were sometimes generated. This is because when the n-type conductive layer 4 contains Al, its lattice constant is reduced.
This is because tensile stress is generated in the mold conductive layer 4.

Therefore, various studies were conducted not only on the buffer layer but also on the underlayer. In the conventional semiconductor light emitting device shown in FIG. 1, as is clear from the structure, the light emitting layer and the like are composed of a nitride semiconductor mainly containing Ga. Therefore, it was naturally considered that the underlying layer for each of these layers was also made of, for example, GaN, mainly Ga-based. As a result, a lattice mismatch with the substrate occurs, and a buffer layer formed at a low temperature is required to alleviate this.

However, the present inventors paid attention to the composition of the underlayer which was supposed to be natural, and tried to change this composition. As a result, they have conceived that the underlayer is composed of a nitride semiconductor mainly composed of Al with low dislocation and good crystal quality. Even if there is no buffer layer, this underlayer can be epitaxially grown on a substrate such as sapphire by complementing a large difference in lattice constant. Further, based on the high crystal quality of the underlayer, the crystal quality of the conductive layer and the light emitting layer formed on the underlayer is also improved, and the dislocation amount thereof is reduced. As a result, the dislocation amount is reduced in each layer constituting the semiconductor light emitting device, and non-radiative recombination due to the high dislocation amount can be effectively suppressed.

Further, such an underlayer having high crystal quality is
Excellent heat dissipation characteristics. Therefore, due to the synergistic effect of the high crystal quality of the underlayer and the heat dissipation characteristic, the light emitting efficiency of the semiconductor light emitting element can be improved, and high brightness light emission is possible.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments of the invention. FIG. 2 is a configuration diagram showing an example of the semiconductor light emitting device of the present invention. The semiconductor light emitting device 20 shown in FIG. 2 includes a base layer 13, an n-type conductive layer 14, a light emitting layer 15, a p-type clad layer 16, and a p-type conductive layer 17 in this order on a substrate 11. Then, similarly to the conventional semiconductor light emitting device 10 shown in FIG. 1, a part of the n-type conductive layer 14 is exposed, and on the exposed n-type conductive layer 14,
For example, an n-type electrode 18 made of Al / Ti is formed, and p
A p-type electrode 19 made of, for example, Au / Ni is formed on the mold conductive layer 15 to form a so-called PIN type semiconductor light emitting device.

In FIG. 2, the n-type conductive layer 14 and the light emitting layer 1
5, the p-type cladding layer 16 and the p-type conductive layer 17 form a nitride semiconductor layer group in the semiconductor light emitting device, and the nitride semiconductor layer group, the n-type electrode 18 and the p-type electrode 19 form a light emitting device structure. Is configured. The p-type cladding layer 16
Can be omitted if desired.

The underlayer 13 is made of Al according to the present invention.
And the dislocation density is 10 ¹¹/ Cm^TwoThe following nitride semiconductors
The dislocation density is
10 more^Ten/ Cm^TwoThe following is preferable. this
In some cases, the lattice constant difference from the substrate 11 is complemented,
In addition to being able to grow epitaxially by itself,
As a result, the n-type conductive layer 14 emits light on the underlayer 13.
The layer 15 and the p-type conductive layer 17 are also grown epitaxially.
Can be made.

Further, the n-type conductive layer 14, the light-emitting layer 15, and the p-type conductive layer 17 constituting the nitride semiconductor layer group contain less Al than the underlayer 13 and have a dislocation density of 10 ¹⁰ /.
It must be composed of a nitride semiconductor of cm ² or less. As a result, the luminous efficiency of the semiconductor light emitting device 20 can be improved.

This is because the ratio of threading dislocations decreases due to the Al composition difference between the underlayer 13 and the n-type conductive layer 14, and
This is because the dislocation density in the type conductive layer 14, the light emitting layer 15, and the p type conductive layer 17 can be reduced, which improves the crystal quality of the n type conductive layer 14 and the like.

The above-mentioned effects become more remarkable as the content of Al in the nitride semiconductor forming the underlayer 13 increases, and the nitride semiconductor contains 50 atomic% or more of all the group III elements. Al is preferably contained, and more preferably AlN is contained.

As described above, the underlayer 13 is formed of the high Al content described above.
The crystal quality of the n-type conductive layer 14 can be further improved by using the nitride semiconductor in the content. As a result, the n-type conductive layer 1 formed on the underlayer 13
4, it is also possible to improve the crystal quality of the light emitting layer 15 and the p-type conductive layer 17 to achieve further low dislocation.

For example, the underlayer 13 is made of AlN, and the n-type conductive layer 14 is formed directly on the underlayer 13.
Is composed of AlGaN or the like containing a relatively large amount of Ga, the underlying layer 13 and the n-type conductive layer 14
Therefore, the dislocation amount of the n-type conductive layer 14 can be further reduced as compared with the dislocation amount of the underlayer 13.

In particular, when the Ga content of the nitride semiconductor layer group is 80% or more with respect to all the constituent group III elements, the n-type conductive layer 1 constituting the nitride semiconductor layer group is formed.
4, the light emitting layer 15, and the p-type conductive layer 17 have a dislocation density of 1 ×
It can be easily reduced to 10 ⁹ / cm ² or less, and can be reduced to 1 × 10 ⁸ / cm ² or less at present. The Ga content is an average composition of the entire nitride semiconductor layer group.

The underlayer 13 made of a nitride semiconductor containing Al and having a low dislocation density and a high crystal quality is, for example, MOCVD.
It can be obtained by controlling the film forming temperature by the method. Specifically, by setting the film formation temperature to 1100 ° C. or higher, it is possible to easily obtain the target underlayer 13 made of a nitride semiconductor of high crystal quality.
The film formation temperature in this patent means the substrate temperature.

N-type conductive layer 1 having low dislocation density and high crystal quality
4 and the like can be inevitably obtained by epitaxially growing the underlayer 13 having low dislocation and high crystal quality by the MOCVD method or the like.

Since the underlayer 13 satisfying the above characteristics is also excellent in heat dissipation characteristics, the light emitting efficiency of the semiconductor light emitting device 20 is further improved by the synergistic effect of high crystal quality and high heat dissipation characteristics. Therefore, high brightness light emission becomes possible.

The substrate 11 is made of sapphire single crystal, ZnO single crystal, LiAlO ₂ single crystal, LiGaO ₂ single crystal, Mg.
Al ₂ O ₄ single crystals, oxide single crystals such as MgO single crystals,
Group IV or IV-IV single crystals such as Si single crystals and SiC single crystals, GaAs single crystals, AlN single crystals, GaN single crystals, and III-V group single crystals such as AlGaN single crystals, Z
It can be composed of known substrate materials such as boride single crystals such as r ₂ B.

In the semiconductor light emitting device of the present invention shown in FIG. 2, the lower conductive layer of the light emitting layer 15 is n-type and the upper conductive layer is p-type. You can also Further, the light emitting layer 15 can be composed of a single nitride semiconductor layer, but can also be composed of a multilayer film such as a multiple quantum well structure.

FIG. 3 is a configuration diagram showing another example of the semiconductor light emitting device of the present invention. Semiconductor light emitting element 3 shown in FIG.
0 indicates the base layer 23 and the n-type conductive layer 2 on the substrate 21.
4, the light emitting layer 25, and the p-type conductive layer 27 are sequentially provided. Then, a part of the n-type conductive layer 24 is exposed, an n-type electrode 28 made of, for example, Al / Ti is formed on the exposed n-type conductive layer 24, and on the p-type conductive layer 27. For example, a p-type electrode 29 made of Au / Ni is formed,
It constitutes a so-called ridge type laser diode.

In FIG. 3, the n-type conductive layer 24 and the light emitting layer 2 are shown.
5 and the p-type conductive layer 27 form a nitride semiconductor layer group in the semiconductor light emitting element, and the nitride semiconductor layer group and the n-type electrode 28 and the p-type electrode 29 form a light emitting element structure.

The underlayer 23 is made of Al according to the present invention.
And the dislocation density is 10 ¹¹/ Cm^TwoThe following nitride semiconductors
The dislocation density is
10 more^Ten/ Cm^TwoThe following is preferable. this
In some cases, the lattice constant difference from the substrate 21 is complemented,
In addition to being able to grow epitaxially by itself,
As a result, the n-type conductive layer 24 and the light emission are formed on the underlayer 23.
The layer 25 and the p-type conductive layer 27 are also grown epitaxially.
Can be made.

Further, the n-type conductive layer 24, the light-emitting layer 25, and the p-type conductive layer 27 constituting the nitride semiconductor layer group contain less Al than the underlayer 23 and have a dislocation density of 10 ¹⁰ /
It must be composed of a nitride semiconductor of cm ² or less. As a result, the luminous efficiency of the semiconductor light emitting device 30 can be improved.

Also in this case, the ratio of threading dislocations is reduced due to the difference in Al composition between the underlayer 23 and the n-type conductive layer 24 as described above, and the n-type conductive layer 24 and the light emitting layer 2 are reduced.
5 and the dislocation density in the p-type conductive layer 27 can be reduced, which improves the crystal quality of the n-type conductive layer 24 and the like.

The above-mentioned effects become more remarkable as the content of Al in the nitride semiconductor forming the underlayer 23 increases, and the nitride semiconductor contains 50 atomic% or more of all the group III elements. Al is preferably contained, and more preferably AlN is contained.

As described above, the underlayer 23 is formed of the high Al content described above.
The crystal quality of the n-type conductive layer 24 can be further improved by comprising the content of the nitride semiconductor. As a result, the n-type conductive layer 2 formed on the underlayer 23
4, it is also possible to improve the crystal quality of the light emitting layer 25 and the p-type conductive layer 27 to achieve further low dislocation.

In particular, the Ga content of the nitride semiconductor layer group is
If the composition is 80% or more of all the group III elements
Is an n-type conductive layer 2 that constitutes the nitride semiconductor layer group.
4, the light emitting layer 25, and the p-type conductive layer 27
1 x 10 as above⁹/ Cm^TwoCan be easily reduced to
Can be done, and currently 1 × 10⁸/ Cm ^TwoUp to
It can be reduced. The Ga content is the same as
2 is an average composition of the entire compound semiconductor layer group.

The underlayer 23 made of a nitride semiconductor containing Al and having a low dislocation density and a high crystal quality is, for example, MOCVD.
It can be obtained by controlling the film forming temperature by the method. Specifically, by setting the film formation temperature to 1100 ° C. or higher, it is possible to easily obtain the target underlayer 23 made of a high-quality nitride semiconductor.
The film formation temperature in this patent means the substrate temperature.

N-type conductive layer 2 having low dislocation density and high crystal quality
4 and the like can be inevitably obtained by epitaxial growth on the underlayer 23 of low dislocation and high crystal quality described above, for example, by the MOCVD method.

Since the underlayer 23 satisfying the above characteristics is also excellent in heat dissipation characteristics, the light emitting efficiency of the semiconductor light emitting device 30 is further improved by the synergistic effect of high crystal quality and high heat dissipation characteristics. Therefore, high brightness light emission becomes possible.

The substrate 21 can be made of sapphire single crystal or the like, like the substrate 11 described above.

In the semiconductor light emitting device of the present invention shown in FIG. 3, the lower conductive layer of the light emitting layer 25 is n-type and the upper conductive layer is p-type. You can also Further, the light emitting layer 25 may be composed of a single nitride semiconductor layer, or may be composed of a multilayer film such as a multiple quantum well structure.

[0045]

EXAMPLE (Example 1) In this example, a PIN type semiconductor light emitting device shown in FIG. 2 was produced. A C-plane sapphire single crystal having a diameter of 2 inches and a thickness of 500 μm was used as the substrate 11, and this was installed in a MOCVD apparatus. MOC
The VD device has H ₂ , N ₂ , TMA, TM as a gas system.
G, Cp ₂ Mg, NH ₃ and SiH ₄ are attached. After setting the pressure to 100 Torr, add H ₂ to the average flow velocity of 1 m.
The substrate 11 was heated to 1150 ° C. while flowing at a rate of / sec.

Then, a predetermined amount of TMA and NH ₃ was supplied to grow an AlN layer as the underlayer 13 to a thickness of 1 μm. At this time, the supply amounts of TMA and NH ₃ were set so that the film formation rate was 0.3 μm / hr. This A
When the dislocation density in the 1N layer was observed by TEM,
It was 8 × 10 ⁹ / cm ² . When the X-ray rocking curve of the (002) plane of AlN was measured, the full width at half maximum was 100 seconds or less, and the surface roughness (ra) was 2Å or less, and it was confirmed to have good crystal quality.

Next, after setting the substrate temperature to 1120 ° C., the pressure was set to normal pressure, TMA, NH ₃ , and SiH ₄ were flowed at an average flow rate of all gases of 1 m / sec to dope Si as the n-type conductive layer 14. The n-GaN layer was grown to a thickness of 3 μm. The raw material supply rate was set so that the film formation rate was 3 μm / hr. SiH ₄ has a carrier concentration of 5 × 10 5.
^It was supplied so as to be ¹⁷ / cm ³ .

Then, the supply of each source gas is stopped and the cap
After changing the rear gas to nitrogen, set the substrate temperature to 700 ° C.
It was TMI, TMG, NH on the n-GaN layer_ThreeTo
Flowing at a total gas flow rate of 1 m / sec as the light emitting layer 15
The i-InGaN layer was formed as an MQW structure. That
After that, change TMI to TMA and Cp ₂Mg
Carrier concentration is 2 × 10¹⁷/ Cm^ThreeSupply as
The p-AlGaN layer as the p-type cladding layer 16 is thickened.
To 20 nm. After that, stop TMA and start
After raising the plate temperature to 100 degrees, TMG, NH_Three, Cp₂
Supply Mg to dope Mg as the p-type conductive layer 17
The p-GaN layer was formed to a thickness of 0.2 μm.

N-GaN layer, i-InGaN layer and p-
When the dislocation density of the GaN layer was observed by TEM,
5 × 10 each⁷/ Cm^Two5 x 10⁷/ Cm ^Twoas well as
5 x 10⁷/ Cm^TwoMet.

Further, the n-type conductive layer 14 is formed by partially removing each of these layers by etching.
-A part of the GaN layer is exposed, and A
An n-type electrode 18 made of 1 / Ti was formed. Further, the p-type electrode 19 made of Au / Ni was formed on the p-GaN layer forming the p-type conductive layer 17.

Comparative Example 1 In this comparative example, the PIN type semiconductor light emitting device shown in FIG. 1 was manufactured. Using a sapphire single crystal substrate as the substrate 1, the same MO as in the example was used.
It was installed in the CVD device. After heating the substrate 1 to 600 ° C., TMG and NH ₃ were supplied to form a GaN layer as the buffer layer 2 with a thickness of 0.03 μm.

After that, the supply of TMG and NH _{3 is} once interrupted, the substrate temperature is set to 1120 ° C., and TMG and N 3 are set.
H ₃ and SiH ₄ are supplied, and n-G as the underlayer 3 is supplied.
The aN layer was formed to a thickness of 3 μm at a film forming rate of 3 μm / hr. Then, similar to the embodiment, the n-type conductive layer 4 to p
By forming up to the type conductive layer 7, an n-type electrode 8 of Al / Ti and a p-type electrode 9 of Au / Ni are formed.
A semiconductor light emitting device 10 was produced.

An n-GaN layer, an i-InGaN layer, and a p that constitute the n-type conductive layer 4, the light emitting layer 5, and the p-type conductive layer 7.
The dislocation density in -GaN layer was measured by TEM observation, each ^{2 × 10 10 / cm 2,} 2 × 10
¹⁰ / cm ² and 2 × 10 ⁹ / cm ² .

FIG. 4 is a graph showing the light emission characteristics of the semiconductor light emitting devices produced in Example 1 and Comparative Example 1 described above. FIG. 4 shows the relationship between the injection current to the semiconductor light emitting element and the light emission output. As is clear from FIG. 4, the semiconductor light emitting device obtained in Example 1 exhibits a larger light emission output than the semiconductor light emitting device obtained in Comparative Example 1 for a given injection current.

Further, it is understood that in the semiconductor light emitting device obtained in Example 1, the light emission output also increases with the increase of the injection current, and the high light emission output is exhibited in the high injection current region. On the other hand, in the semiconductor light emitting device obtained in Comparative Example 1, it was found that the device was destroyed in the high injection power region, and the light emission output was deteriorated accordingly.

Example 2 In this example, a simplified version of the ridge type laser diode shown in FIG. 3 was produced. Specifically, the light emitting layer 25, the p-type conductive layer 27, n
The underlying layer 23 was made to function as a light emitting layer without forming the mold electrode 28 and the p-type electrode 29, and stimulated emission was carried out by using predetermined excitation light.

The substrate 21 has a diameter of 2 inches and a thickness of 500 μm.
A m-plane C-plane sapphire single crystal was used and placed in a MOCVD apparatus. The MOCVD apparatus uses H ₂ , N ₂ , TMA, TMG, Cp ₂ Mg, NH ₃ , and SiH as a gas system.
₄ is attached. After setting the pressure to 100 Torr, while flowing H ₂ at an average flow rate of 1 m / sec, the substrate 2
1 was heated to 1150 ° C.

After that, a predetermined amount of TMA and NH ₃ was supplied to grow an AlN layer as the underlayer 23 to a thickness of 1 μm. At this time, the supply amounts of TMA and NH ₃ were set so that the film formation rate was 0.3 μm / hr. This A
When the dislocation density in the 1N layer was observed by TEM,
It was 8 × 10 ⁹ / cm ² . When the X-ray rocking curve of the (002) plane of AlN was measured, the full width at half maximum was 100 seconds or less, and the surface roughness (ra) was 2Å or less, and it was confirmed to have good crystal quality.

Next, after setting the substrate temperature to 1120 ° C., the pressure was set to normal pressure, TMG, NH ₃ , and SiH ₄ were flowed at an average flow rate of all gases of 1 m / sec to dope Si as the n-type conductive layer 24. The n-GaN layer was grown to a thickness of 3 μm. The raw material supply rate was set so that the film formation rate was 3 μm / hr. SiH ₄ has a carrier concentration of 1.1 ×
It was supplied so as to be 10 ¹⁷ / cm ³ .

Thereafter, the assembly produced as described above was cleaved to a length of 3000 μm to produce a ridge type laser diode having a width of 500 μm. The n-GaN
When the dislocation density of the layer was observed by TEM, it was 5 × 1.
It was 0 ⁷ / cm ² .

Comparative Example 2 In this comparative example, a ridge type laser diode was manufactured in the same manner as in Example 2. However, when the substrate 21 is heated to 600 ° C. and TMG and NH ₃ are supplied, G as a buffer layer is formed on the substrate 21.
The aN layer was provided to a thickness of 0.03 μm. At this time, the dislocation density of the n-GaN layer formed on the buffer layer was measured by TEM.
It was 2 × 10 ¹⁰ / cm ² when observed by.

When the relationship between the stimulated emission light output and the excitation light intensity of the laser diodes obtained in Example 2 and Comparative Example 2 was examined, the results shown in FIG. 5 were obtained. In the laser diode shown in Example 2 obtained according to the present invention,
Stimulated emission occurs at an excitation light intensity of 0.5 MW / cm ² , whereas in a laser diode having a low temperature buffer layer as shown in Comparative Example 2, stimulated emission occurs at an excitation light intensity of 0.6 MW / cm ^2. It was confirmed to occur. That is, it was confirmed that in the laser diode of Example 2 obtained according to the present invention, the threshold value at which stimulated emission occurs was reduced, and the excitation efficiency was high.

As is clear from the above examples and comparative examples, in the semiconductor light emitting device manufactured according to the present invention, the crystal quality of each layer is improved due to the high crystal quality of the underlayer, and the dislocation amount is reduced. It can be seen that the luminous efficiency and the excitation efficiency are improved by the synergistic effect of the effect described above and the effect of improving the heat dissipation characteristic of the AlN underlayer, and high-luminance light emission is realized. Therefore, it was confirmed that the semiconductor light emitting device of the example is a highly efficient semiconductor light emitting device and can emit light with high brightness as compared with the semiconductor light emitting device of the comparative example.

Although the present invention has been described in detail with reference to the embodiments of the invention with reference to specific examples, the present invention is not limited to the above contents and does not depart from the scope of the present invention. All modifications and changes are possible as long as possible.

For example, nitriding treatment may be applied to the substrate, or III
Pretreatment of the substrate with a group material can also be performed.
It is also possible to change the composition of the underlayer continuously or to change the film forming conditions in stages. Further, for the purpose of further improving the crystallinity of the conductive layer or the light emitting layer, a multilayer laminated structure such as a buffer layer or a strained superlattice is provided between the underlayer and the conductive layer, such as temperature, flow rate, pressure, raw material supply amount, Also, it can be inserted by changing the growth conditions such as the additive gas. In addition, n below the light emitting layer
An n-AlGaN cladding may be inserted on the layer side. It is not necessary to perform film formation for each layer in the same film forming apparatus.
Other devices may be used.

The underlayer is made of Ge, Si, Mg,
Additional elements such as Zn, Be, P, and B can also be contained. Furthermore, not only the elements that were intentionally added, but trace elements that are inevitably incorporated depending on the film formation conditions,
In addition, trace amounts of impurities contained in the raw materials and reaction tube materials may be included.

The semiconductor light emitting device of the present invention can be used not only for the PIN type semiconductor light emitting device described above, but also for any type of semiconductor light emitting device.

[0068]

As described above, in the semiconductor light emitting device of the present invention, since the underlayer is composed of a nitride semiconductor containing Al and having a low dislocation density and a high crystal quality, a conventional buffer layer is used. It is possible to supplement the lattice constant difference with the substrate and to grow the conductive layer and the light emitting layer epitaxially without the need for Further, the crystallinity of the conductive layer, the light emitting layer and the like can be improved and the dislocations can be reduced based on the high crystal quality of the underlayer.

As a result, the semiconductor light emitting device of the present invention has a light emitting device structure composed of a group of nitride semiconductor layers having a low dislocation density, so that the luminous efficiency can be improved in actual use. .

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a conventional semiconductor light emitting device.

FIG. 2 is a configuration diagram showing an example of a semiconductor light emitting device of the present invention.

FIG. 3 is a configuration diagram showing another example of the semiconductor light emitting device of the present invention.

FIG. 4 is a graph showing emission characteristics of a semiconductor light emitting device.

FIG. 5 is a graph showing the relationship between stimulated emission output from a ridge-type GaN film and excitation light intensity.

[Explanation of symbols]

1,11,21 substrate, 2 buffer layers, 3,13,2
3 underlayer, 4, 14, 24 n-type conductive layer, 5, 15,
25 light emitting layer, 6,16 p-type cladding layer, 7, 17,
27 p-type conductive layer, 8, 18, 28 n-type electrode, 9, 1
9,29 p-type electrode, 10,20,30 semiconductor light emitting device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Oda Osamu             2-56, Sudacho, Mizuho-ku, Nagoya-shi, Aichi             Inside Hon insulator Co., Ltd. (72) Inventor Takashi Egawa             2-14 Kozakura-cho, Showa-ku, Nagoya-shi, Aichi Prefecture             6 F-term (reference) 5F041 AA40 CA05 CA34 CA40 CA46                       CA65                 5F073 AA13 AA74 CA07 CB05 CB07                       DA05 DA35 EA29

Claims (6)

[Claims] 1. A semiconductor light emitting device comprising a base layer made of a nitride semiconductor and a light emitting device structure including a group of nitride semiconductor layers on a predetermined substrate, wherein the nitride forming the base layer. The semiconductor contains at least Al and has a dislocation density of 10 ¹¹ / cm ² or less, and the nitride semiconductor layer group forming the light emitting device structure contains less than the nitride semiconductor forming the underlayer. Al is contained in an amount, and the dislocation density is 1 × 10
^A semiconductor light-emitting device characterized by having a density of ¹⁰ / cm ² or less. 2. The semiconductor light emitting device according to claim 1, wherein the nitride semiconductor forming the underlayer has an Al content of 50 atomic% or more with respect to all group III elements. 3. The semiconductor light emitting device according to claim 2, wherein the nitride semiconductor forming the underlayer is AlN. 4. The semiconductor light emitting device according to claim 1, wherein the nitride semiconductor forming the underlayer is formed by MOCVD at a temperature of 1100 ° C. or higher. . 5. The Ga content of all the group III elements in the nitride semiconductor layer group constituting the light emitting device structure is 80%.
It is above, The semiconductor light-emitting device as described in any one of Claims 1-4 characterized by the above-mentioned. 6. The nitride semiconductor layer group forming the light emitting device structure includes an n-type conductive layer, a p-type conductive layer, and a light emitting layer, and the light emitting layer is the n type conductive layer on the substrate. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is located so as to be sandwiched between the p-type conductive layer and the p-type conductive layer.